The need for marine biodiversity conservation -- What is where and how much of it is there? the role of science -- Ecosystem structure, functioning and viability -- Understanding change -- Impacts of human activities on ecosystem composition, structure and function -- The application of science to management : introduction -- "Threatened" and "sensitive" species and habitats -- Sampling and recording -- Selection, design and management of marine protected areas -- Assessing likely impacts and monitoring change -- Recovery, restoration and replacement of habitats and species -- Conclusions and the manager's "toolbox" -- Glossary.